#include<stdio.h>
#include<math.h>
int main()
{
    double e=0.1,b=0.5,c,d;
    long int i;
    for(i=6; ;i*=2){
        d=1.0-sqrt(1.0-b*b);
        d=0.5*sqrt(b*b+d*d);
        if(2*i*b-i*e<1e-15)
        break;
        e=b;
    }
    printf("pai=%.15lf\n",2*i*b);
    printf("The number of edges of required polygon: %ld\n",i);
}